Axis Products' HVLP Spray Systems - A New Way To Spray

A New Way To Spray And Live Another DayLike many of you, we aren't professional automotive painters, but that doesn't stop us-or most of you, for that matter-from giving something new the "old college try," as it were, like wielding a spray gun. Over the last year we have been bringing you body and paint basics stories, some of which were familiar territory to begin with, but much were new to us as well, which in our opinion is often the most fun. After all, if we aren't continually learning, what's the point?

HVLPHVLP painting has been around for more than a few decades now; in fact, HVLP was basically born from old canister vacuums that could be reversed and blow air, and eventually you could order a spray gun of sorts with your vacuum to paint your house...or even your automobile! Obviously, the process and equipment have been far improved from those days, and there's no doubt that the majority of you have heard if not used an HVLP spray gun by now, but what is HVLP, exactly? HVLP (high volume low pressure) guns use much less pressure to push the paint into the air stream, where it is atomized by a higher volume of lower-pressure (10 psi or less) air. HVLP spray guns are accepted as superior to conventional paint guns for many reasons, including anywhere between 40 and 60 percent less (depending on who you ask) material usage. That means significant material/money savings because the paint is going directly to what you are spraying instead of in the air. This increased efficiency is better for the environment as well as your pocketbook. Some HVLP guns work with an air compressor and some with a turbine, so which should you use?

Air Compressors And HVLPAn air compressor uses pistons or a diaphragm to push a relatively small volume of air at high pressure into a holding tank. Until about 15 years ago, most spray guns required an air compressor. The air compressor is capable of pressures of 125 psi and more, but are heavy, and can produce contaminated air when they are worn out or improperly filtered.

But one of the biggest problems many of us non-pros face when it comes to automotive painting is not having the optimum tools or equipment to do the job right, and having an adequate air compressor is on the top of the list, especially for non-HVLP users. To run a non-HVLP gun, you generally need at least a 5hp compressor and a minimum 20-gallon air tank; for an HVLP gun you'll need about 3 hp and a 20-gallon tank.

On top of the proper air compressor you'll need a quality, genuine HVLP gun-not a swap meet or cheapo one, as most often these are converted conventional guns-a regulator, air filters, an inline evaporator, and, of course, an air hose. You'll also need a high-quality respirator or even a fresh air respirator since the paint industry knows so much now about all the bad stuff in paint that is known to cause diseases such as silicosis, isocyanate poisoning, emphysema, and even cancer that can be directly attributed to breathing air contaminated with toxic vapors and mists. Anyone around paints has been subject to and is at risk for all the above-which is a whole 'nuther story...more on this later. Each and every one of these things adds up to quite a bit of money, not to mention space. Even though those giant compressors at the home improvement store look impressive, not all of us have the room for one, so what about turbines?

Turbine HVLPA turbine is a high-speed centrifugal blower motor that provides the gun with high cfm flow at low pressures. Because of the high rpm (near 20,000 rpm in some cases) a turbine operates at, the air is frictionally heated. This heat serves to eliminate all moisture from the atomizing air. The high rpm also increases the atomizing air temperature, which reduces flash time. Turbines are also lightweight and provide a reliable source of dry, oil-free air, unlike an air compressor on its own.

AXIS Products offers a high-quality turbine HVLP system-with a twist. Until now, a person using either a turbine or air compressor HVLP system was faced with hooking up a separate fresh air respirator along with whichever paint system to receive adequate breathing protection. It seems to be widely known that most non-professional air purifying respirator devices fail to protect a person's health in today's painting environment. To solve the problem, Axis Products developed their Citation HVLP sprayer/respirator system which combines the sprayer and fresh air system into one compact, economical package so you'll never be without fresh, clean, dry air whenever you paint or sand/grind hazardous materials.

I was totally in the dark about turbine HVLP systems, so I called and spoke with Jan from AXIS Products at length to bring me up to speed and educate me. One of the first things I asked her was if you can use an HVLP gun designed to be used with an air compressor, and she informed me that guns for each system are specific, but there are adapters to use a turbine gun with a compressor, but not the other way around. Turbine guns differ from conventional spray guns in two main areas. First is the size of the internal air ports. Compressor-type spray guns' internal air port openings are approximately 1/4-inch in diameter, while turbine guns need more air and use 5/8-inch air ports, more than six times larger than those in compressor guns. Keep in mind that HVLP atomizes with a high volume of air and low pressure. The second major difference is the manner in which the material is moved from the cup out of the nozzle. Turbine HVLP units pressurize the cup, forcing material to the nozzle. A conventional gun creates a vacuum to siphon material to and through the nozzle.

Jan also went on to say that the spray gun makes all the difference with any system, and AXIS is always on the search for the perfect gun since they don't manufacture their own and are dependent on what's on the market. So far they are pleased with and continue to supply the Accuspray guns by 3M, but when new spray guns become available, they continue to test them.

Next to the turbine itself and the gun, the other key ingredient for a quality turbine HVLP system is the often ignored air hose. Obviously, its function is to transfer air from the turbine to the spray gun and from the turbine to the respirator. The hose used with the AXIS sprayers is specifically designed to withstand heat and solvents, while remaining lightweight and pliable so you can easily maneuver around what you are spraying. A 20-foot hose is standard on AXIS products and should be long enough for most, but you can double it if needed, though 40 feet is the limit. psi drops at the gun with a longer hose, and since we're dealing with 5 1/2 psi with a Citation 3, there isn't much to lose.

Although there are many variations and uses, the main function of a turbine in HVLP equipment is to generate a high volume of air at pressures less than 10 psi. A critical element in determining the amount of air pressure that a turbine can generate is the number of stages that it has. A stage within a turbine can be thought of as a water wheel, and the higher the number of stages (or water wheels), the higher the psi the turbine can generate. And the higher the static pressure, the higher the viscosity of material that can be sprayed. While airflow (cfm) and pressure (psi) are both important in determining the turbine's ability to atomize coatings, pressure is the key. All manufacturers rate their turbines in the range of 50-170 cfm, and whether the turbine produces 50 or 170 cfm, it will still have enough airflow to support the gun, which only uses about 25 cfm. Therefore, cfm as a measure of performance can be misleading. Pressure determines the velocity of the air moving to the fluid nozzle in the gun.

I asked Jan if there were any drawbacks to a turbine system like their Citation units. The only thing she could think of was that users need to keep in mind to reduce their paints 10-20 percent more than what the manufacturer recommends because of the hotter air produced by the turbine, which causes the paint to flash faster, leading to a rougher orange peel finish. Once the user gets used to the additional reduction needed, they'll be quite happy with the system and can produce award-winning finishes with enough painting experience, not to mention literally breathing easier and staying healthy.

We were convinced and intrigued by the new-to-us HVLP turbine way of painting, so we talked the fine folks over at Paint'n Place down the road here in Placentia, California, into letting us take over one of their paint booths for an afternoon to try our hand at AXIS' Citation 3 paint sprayer and respirator. Jerry, the shop's owner, was so impressed with the Citation versus the old turbine units he remembers using back in the day that we're going to let him borrow it when we're done. We'll have to do a follow-up story with him on our website, www.classictrucks.com. In the meantime, give AXIS a call for more info.